Backscatter Antenna Impedance Modulation for Low-Power Wi-Fi

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Solution Overview

Problem

Existing communication technologies consume excessive power, making it difficult for devices to connect to the Internet efficiently, especially for those relying on energy harvesting, and ambient backscatter technologies often create isolated networks disconnected from the Internet.

Innovation Solution

The system employs endpoint devices that modulate wireless communication signals by controlling the impedance of an antenna to reflect or absorb signals, allowing for low-power communication with access point devices, enabling Internet connectivity using conventional wireless communication standards like Wi-Fi, even for power-harvesting devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional radio communication is used, then communication functionality is achieved, but power consumption increases significantly

Engineering Contradiction:

Improvepower consumptionVSAvoidcommunication reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent replaces the conventional mechanical/electronic transmission system with an electromagnetic field-based backscatter system. The endpoint device modulates the ambient RF field to communicate data without generating its own radio signals, thereby substituting a high-power transmission mechanism with a low-power reflection/modulation mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an ambient RF field as an intermediary carrier for communication. Instead of the endpoint device directly transmitting signals, it modulates the ambient RF field which then carries the information to the receiver, reducing the power requirements of the endpoint device.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If ambient backscatter technology is used, then power consumption is reduced, but network connectivity to the Internet is lost

Engineering Contradiction:

Improvepower consumptionVSAvoidnetwork connectivity

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The patent makes the backscatter communication system universally compatible with existing Wi-Fi and other wireless networks. The endpoint device can communicate using standard wireless protocols while maintaining Internet connectivity, allowing the same low-power mechanism to work across multiple network infrastructures rather than creating isolated networks.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If conventional Wi-Fi transceivers are used, then Internet connectivity is achieved, but power requirements exceed available harvested energy

Engineering Contradiction:

ImproveInternet connectivityVSAvoidpower requirement

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent applies partial action by having the endpoint device perform only the minimal necessary modulation of the RF field for communication, rather than full transmission. The endpoint device modulates the ambient field just enough to convey information while the access point handles the bulk of the communication power requirements, enabling operation with harvested energy.

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach facilitates very low-power wireless networking, allowing power-harvesting devices to communicate with commodity Wi-Fi devices, providing Internet connectivity while minimizing power consumption and maintaining network connectivity.

Implementation Method 1

modulating a channel associated with the wireless communication signals by utilizing a switch to control an impedance of an antenna to either reflect or absorb wireless network communication signals received by the endpoint device

Methodology Applied

Scientific EffectImpedance control: Electrical Impedance Tomography

Implementation Method 2

devices employing power harvesting (e.g. RF power harvesting) for power

Methodology Applied

Scientific EffectPower harvesting: Photovoltaic Effect

Data Source

PatentUS10382161B2Wireless networking communication methods, systems, and devices operable using harvested power

Publication Date: 2019.08.13 UNIV OF WASHINGTON

AI summary

Example devices described herein include endpoint devices which may communicate with an access point device by modulating a channel associated with the wireless communication to encode transmit data. The channel modulation may be performed by utilizing a switch to control an impedance of an antenna at the endpoint device to either reflect or absorb wireless network communication signals received by the endpoint device. The access point device may extract the transmit data by decoding changes in the channel caused, at least in part, by the modulation. Access point devices may transmit a pattern of packets—the presence or absence of which may correspond with transmit data. Endpoint devices may decode this data by using an energy detector to differentiate between the presence or absence of a packet.